1. Field of the Invention
The present invention is related to the field of conveyor belts. More specifically, the invention relates to conveyor belt drive mechanism that are self-cleaning.
2. Description of Related Art
Conveyor systems having a conveyor belt are commonly used in various industrial fields for material handling and processing purposes. Many of these conveyor systems have conveyor belts that include linkages or connecting rods which interconnect numerous overlay elements together to form the conveying surface area of the conveyor belt. Such conveyor belts are typically driven by a drive mechanism which includes a motor driven drive gear with a plurality of teeth that engage and drive the linkages or connecting rods of the conveyor belt. For example, U.S. Pat. No. 5,934,448 to Kucharski et al. discloses a conveyor belt including a plurality of wickets which are interconnected by rods whereby a drive sprocket drives the conveyor belt by engaging a sprocket-engagement area on the rods.
Increasingly, conveyor belts are used in manufacturing processes where the items being conveyed are frequently processed on the conveyor belt itself while being conveyed from one location to another. For example, in the food processing industry, processes including washing, cooling and freezing of food items as well as other processes are frequently done directly on the conveyor belt as the food items are being conveyed. Because the food items are processed directly on the conveyor belt, food processors have found that efficient use of both time and space may be realized. In this regard, conventional drive mechanisms using a drive gear have been found to be inadequate in many processing applications where the grooves between the teeth of the drive gear can become clogged.
For instance, items or portions of items being conveyed can become lodged in the grooves between the teeth of the drive gear. This has been especially problematic in applications where the items being conveyed are very small and also in the food industries where small portions of the food items being conveyed tend to break off onto the conveying surface of the belt, these small portions eventually lodging in the grooves of the drive gear. Over time, these small portions of the food items tended to build up and clog these grooves. Also in the food industry, conveyors are used in freezing processes where the food item is conveyed into a freezing chamber and blasted with freezing air to instantly freeze the food item being conveyed. It has been found that in such applications, ice tends to build up in the grooves of the drive gear. As can be appreciated, when the grooves between the teeth of the drive gear become clogged, the drive gear can no longer engage the linkages or connecting rods of the conveyor belt thus rendering the conveyor belt inoperative until the grooves of the drive gear is unclogged of the food, ice, or other debris. Of course, accumulation of debris in the grooves of the drive gear is a problem experienced not only in the food industry, but also in many different industries that utilize conveyor belts.
In an attempt to address such problems, U.S. Pat. No. 2,784,836 to Le Tourneau discloses a self-cleaning sprocket including a plurality of teeth with an inclined recess between each pair of teeth. The inclined recess aids in keeping the teeth of the sprocket clean as it engages the pins. In addition, other self-cleaning drive mechanisms have also been created. For instance, a self-cleaning drive mechanism has been designed with a drive gear having a plurality of teeth that engage and drive the linkages or connecting rods of a conveyor belt. In this regard, each of the plurality of teeth includes a receiving groove that receive a linkage or a connecting rod and exert a displacing force on the linkage or connecting rod thereby displacing the conveyor belt. The self-cleaning drive mechanism also typically includes a motor for driving the drive gear as well as other support members that support the drive gear in proper position.
Moreover, receiving grooves for the self-cleaning sprocket have been designed to facilitate the self-cleaning feature. In particular, a bottom surface of the receiving groove of each of the plurality of teeth may be chevron shaped and have tapered relief surfaces. In operation, as the linkage or connecting rod of the conveyor belt is engaged by the receiving groove, the linkage or connecting rod forcibly displaces any debris that may be present in the receiving groove. The displacement of the debris is facilitated by the tapered relief surfaces so that as the linkage or connecting rod contacts the bottom surface, the debris is forced out of the receiving groove. The above described prior art self-cleaning drive mechanism has been found to be effective in various applications where the debris caught in the receiving groove is relatively soft such as soft food items. However, the prior art self-cleaning drive mechanism has been found to be inadequate where the debris or debris build-up is relatively hard.
In particular, the present applicants have found that when the debris or debris build-up is hard, such as frozen food particles and ice build-up in applications where the conveyor is used for freezing processes, the linkage or connecting rod engaging the receiving groove did not exert enough force on the debris to displace the debris when conventional amount of tension is placed on the conveyor belt. Thus, in such freezing process applications, such prior art drive mechanisms have been found to be unreliable and inadequate. The applicants sought to increase the tension placed on the conveyor belt to thereby increase the force exerted by the linkage or connecting rod. Whereas this appeared to improve the situation, it was found that such increase in conveyor belt tension increased wear on the conveyor belt and thus, decreased the belt's durability. Of course, to alleviate this disadvantage, the conveyor belt itself could be made more robust and durable. However, such improvements in the belt would be very expensive due to the increased material cost and weight which would require a more robust drive mechanism and components such as the motor and the other support members.
Therefore, there exists an unfulfilled need for an improved self-cleaning drive mechanism for driving a conveyor belt which will clean hard debris and even ice build-up. There also exists an unfulfilled need for such a self-cleaning drive mechanism which will clean such debris and build-up in a reliable and cost effective manner.